Coronary air embolism (CAE), a known but infrequent complication of cardiac bypass, was studied as an ischemic injury in two groups of sheep. The distribution of myocardial blood flow (MBF - measured with radioactive microspheres) and hemodynamic parameters were measured before and after injection of 1 ml of air into the proximal circumflex coronary artery. MBF was compared in embolized and normal myocardium. CAE caused marked transient decreases in mean MBF with redistribution (R) of blood flow away from the subendocardium. A hypermic recovery period was seen within 15 minutes of CAE with recovery of all measured parameters except dp/dt within 30 minutes. Rapid restoration of arterial pressure with dopamine resulted in significantly increased mean MBF, initially associated with (R). (R) is superseded within 5 minutes by subendocardial hyperemia with continued dopamine infusion.